A wrist that has been damaged by an injury or has been affected by a disorder such as arthritis may produce pain and may not function properly. In severe cases, patients may suffer from severe wrist pain and can lose the ability to use the wrist. Previously, such severe wrist conditions that were unresponsive to other treatments were addressed with a procedure known as wrist arthrodesis. The procedure fuses the bones of the wrist together to reduce or eliminate pain. However, if the bones are fused together, movement of the wrist is severely limited or lost.
Total wrist replacement surgery, also known as total wrist arthroplasty, replaces the damaged wrist joint with a prosthetic wrist implant. Unlike wrist arthrodesis, a wrist replacement eliminates pain without compromising wrist movements. U.S. Pat. Nos. 5,702,470 and 6,059,832 describe a prosthetic wrist implant disposed between a patient's radius and carpal complex bones. The implant includes a radial implant component, a carpal bone implant component, and an articulating bearing member that is fastened to the carpal bone implant component and slidingly engages the radial implant component. The articulating bearing member of these patents can be designed to connect laterally (sideways from the dorsal plane) onto the carpal bone implant component through the use of slots on the bearing member that connect with tabs on the carpal bone implant component.
Alternatively, in patients with severe arthritis who do not qualify for total wrist arthroplasty but request an alternative to complete wrist fusion, a procedure called radial hemiarthroplasty can be used. In this procedure, only the radial component of a total wrist arthroplasty system can be used.
Although the existing prosthetic wrist implants can relieve pain without causing loss of wrist movement, it is desirable to provide improved prosthetic wrist implant components and systems having enhanced stability and a greater degree of movement or freedom in the joint.